Capsule technology continues to be subject to development and improvements. Such capsules typically come in two main forms, either in the form of hard capsule shells or in the form of soft capsules (also referred to as softgels or soft gel capsules).
Hard capsule shells are generally manufactured using dip molding processes involving the use of pins dipped into solutions of the different ingredients that are needed for the making of the capsule shell containers. Methods for the manufacturing of soft gelatin or softgel capsule shells are also known in the art and are different from hard capsule shell manufacturing. Manufacturing of soft gelatin or softgel capsule shells at a production scale was introduced by Robert Pauli Scherer in 1933 with the invention of a rotary die encapsulation machine. The rotary die process involves continuous formation of a heat seal between two ribbons of gelatin (also referred to as “gel mass” since it may contain plasticizers as listed below) simultaneous with dosing of the fill liquid into each capsule. Although manufacturing process speed and efficiency has improved with time, the basic manufacturing principle remains essentially unchanged. Before the encapsulation process takes place, two sub-processes are often carried out simultaneously, yielding the two components of a softgel capsule: (a) the gel mass which will provide the softgel capsule shell, and (b) the fill matrix for the softgel capsule contents. Softgel capsules have a continuous gelatin shell surrounding a liquid core, and are formed, filled, and sealed in one operation.
Softgel capsule walls are typically thicker than two-piece hard gelatin capsules, and their walls comprise plasticizers such as, for example, glycerol, sorbitol and/or propylene glycol to make the shell elastic. Processes for making softgel capsule shells are known, and softgel capsules are available commercially. See, e.g., Aulton, M., Aulton's Pharmaceutics: The Design & Manufacture of Medicines, 527-533 (Kevin M G Taylor, Ed., 3rd Ed., 2001). Softgel capsules have various advantages; they may show improved drug absorption, be easier to swallow, avoid dust handling issues, and have increased stability compared to other dosage forms. Softgel capsules may be filled with liquid fill such as but not limited to oils and/or lipid soluble active ingredients such as pharmaceuticals, veterinary products, foods and dietary supplements. Highly viscous products, pastes and solids such as powders may also be filled.
Typical materials for both hard capsules and softgels include gelatin (of various sources including bovine, porcine, poultry, and/or fish) or non-gelatin materials such as synthetic polymers and/or plant-derived hydrocolloids. Gelatin is favorably used as shell forming material, particularly of softgels, due to its unique physiochemical properties, namely its oxygen impermeability and the combination of film-forming capability and thermoreversible sol/gel formation, that favor its use for the industrial capsule production, especially the softgel production via the rotary die process.
Although both hard and soft capsules are capable of storing liquids therein, softgel capsules may be desirable in view of their capability of storing liquid fills without requiring additional sealing procedures, as well as in some instances provide stability advantages when utilizing certain fills in view of the higher plasticizer content. The plasticizer content in softgels may further bring resistance to brittleness and/or improved administration in applications such as vaginal or rectal administration.
It is often desirable to print capsules with indicia such to provide identification of the brand or type of product or production number and the like information thereon. This is typically done with a water-based ink.
Such common printing processes, however, do result in the production of a number of defect prints over a population of printed capsules, particularly when operating at high production speeds. This leads to a number of waste (or reject) product being generated. Particularly for softgels, where the printing is to be carried out post-filling. The rejected dosage forms can quickly result in costly scrap, particularly when the liquid fill comprises expensive pharmaceutically active substances.
A need therefore exists to provide a new printing process that limits such drawbacks, particularly in post-liquid-filling printing.